<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        /* 如果有标签选择器必须写在最前面 */
        p.box {
            color: red;
        }
    </style>
</head>
<body>
    <p class="box">
        div
    </p>
    
    <p>
        p1
    </p>

    <div class="box">
        p2
    </div>
</body>
</html>